This application proposes to study the mechanisms of regulation of glycogen synthesis in heart tissue. The objectives of the research include determining the molecular structure of glycogen synthase from bovine heart and the importance of this structure to regulation of the enzyme. We will also determine the role of multiple phosphorylation sites of this enzyme in the interconversion of the enzyme between two physiologically important forms. A second objective will be to purify and study the regulation of heart protein phosphatase(s). At least two forms of the phosphatase(s) will be subjects of interest and a factor important to glycogen inhibition of glycogen synthase phosphatase will be studied also. A third objective of the study will be to relate the control of the enzymes of glycogen metabolism to the function of these enzymes in cell culture. These studies will use heart cells for studies on the role of hormones and glucose in regulation of protein phosphatases and in the regulation of glycogen synthesis.